1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display that may have wide viewing characteristics and be capable of fast driving.
2. Discussion of the Background
A liquid crystal display (LCD) may have non-uniform display characteristics at different viewing angles and inferior display quality of a moving image due to motion blur.
Therefore, various structures and driving methods have been suggested to decrease viewing angle dependency and improve the quality of moving images.
In a two thin film transistor (TFT) (T-T) structure, a pixel electrode is divided into a main-pixel electrode and a sub-pixel electrode, and different data voltages are applied to each electrode so that a voltage difference between two liquid crystal capacitors is generated. In a coupling capacitor (C-C) structure, a data voltage is applied to a main-pixel electrode and a sub-pixel electrode is capacitively coupled with the main-pixel electrode so that a voltage difference between two liquid crystal capacitors is generated. The T-T structure and the C-C structure are representative examples of a structure that may decrease viewing angle dependency.
But, in the T-T structure, the aperture ratio and the driving margin may be reduced because there are twice as many data lines or gate lines, and the manufacturing cost may increase due to the high price of multi-channel ICs.
In the C-C structure, the brightness may be reduced because the voltage of the sub-pixel electrode coupled with the main-pixel electrode may be low in comparison with the data voltage. Also, the degree to which viewing angle dependency may be reduced may be limited because the voltage of the sub-pixel electrode is determined by the capacitance ratio of insulating layers.
Korean Patent Application Nos. 2003-0056546, 2006-0071762, and 2007-0121092 are examples of charge sharing (CS) structures that may be able to solve the problem of the prior art described above. The CS structure may decrease viewing angle dependency without increasing the number of gate lines or data lines.
A 120 Hz fast driving technology, which has recently been applied to commercial products, is a representative example of a driving method that may improve the display quality of a moving image. Because applying the 120 Hz fast driving technology may reduce the charging margin of the liquid crystal capacitor by half, the so-called pre-charging driving technology, in which turn-on times of neighboring gate lines overlap each other, is generally applied for compensation while column inversion driving is applied. If a 180 Hz (or more) fast driving technology is applied to a LCD having a full-high definition (full-HD) resolution, applying the pre-charging driving technology may be inevitable.
Because a pre-charging driving technology is operated such that turn-on times of neighboring gate lines overlap each other, if this driving method is applied to the CS structure, in which charge-sharing is carried out when a next neighboring gate line is turned on, differentiating the voltages between two sub-pixel electrodes may not occur properly so the viewing angle dependency may not be decreased.